W = slEquivariantVectorBundle(n,m,d,CoefficientRing=>C)
This is an option to tell slEquivariantVectorBundle to define the vector bundle over a projective space whose coordinate ring has coefficients in the ring C.
The source of this document is in /build/reproducible-path/macaulay2-1.25.06+ds/M2/Macaulay2/packages/SLnEquivariantMatrices.m2:898:0.